While no definite conclusions can be drawn from the few larvae of Ho- 

 lothurians hitherto known, and likewise the Crinoids are out of question 

 in this connection having no true pelagic larvae, the Ophiuroid larvae have 

 an important bearing on the problem. Larvae belonging to the genera 

 Ophiothrix, Ophiopholis, Ophiadis and Amphiura are known but only one 

 of each genus. They do not afford so very characteristic differences as 

 one should expect, since they belong to three different families, and 

 those of Ophiopholis and Ophiadis are more different than should be 

 expected after the apparently near relation of these two genera. Then 

 within the genus Ophiura we know with certainty the larvae of the two 

 species Oph. albida and texturata, and these are so different that one would 

 rather think they must belong to different famiUes. The larvae which are 

 with a considerable degree of probability referred to Oph. affinis and 

 Homalophiura gelida (Koehler) again are very different from each other 

 as well as from the two named above. — These facts are thus decidedly 

 opposed to the conclusions to be drawn from our previous knowledge of 

 the Echinoid and Asteroid larvae. Considering, however, that our knowledge 

 of the natural affinities of the vast number of Ophiurids is still rather 

 unsatisfactory, even in spite of the more recent attempt at a natural 

 classification of this group byMatsumoto, it seems to me that the 

 facts known of the Echinoid and Asteroid larvae outweigh those of the 

 Ophiuroid larvae, and lead to the conclusion that these larvae, on the con- 

 trary, tend to prove that there is something wrong with our classification 

 of the Ophiuroids. 



In spite of these Op/ii tzr a-larvae it seemed then a legitimate conclusion that 

 the Echinoderm larvae are really of considerable classificatory value, the 

 larvae of nearly related forms agreeing in their main characters; the opposite 

 conclusion would then be equally legitimate, that when the larvae of two 

 forms, apparently nearly related, prove to be essentially different, those 

 forms are not in reality nearly related. The study of the larval forms will 

 then afford a very important test for the value of our classification of 

 the adult forms. 



It is evident that the knowledge of a very much larger number of 

 Echinoderm larvae than the comparatively few known till now is required 

 for placing the idea of the classificatory value of these larvae on a more 

 firm base. Nearly all the researches hitherto made on the development 

 and the larval forms of Echinoderms were carried out on species occurring 

 in the European and North American Seas, only a few forms from the 

 tropical seas of America having more recently been made the object of 

 study (Tennent). But, moreover, it is mainly a few selected types 

 which have, over and over again, been studied, so that even of the com- 



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